Shorthand for Service UDP/DNS?

[yary]

I see the shorthand for UDP/Domain ("Service UDP/Domain/example.com")
documented at http://argus.tcp4me.com/services.html

And one example under http://argus.tcp4me.com/xtservices.html shows a
shorthand for Service UDP/DNS: "UDP/DNS/Serial/example.com" - but I
can't find documentation of that abbreviation.

How does that work?